WBJEE paper 2 consist of Physics and Chemistry. If you are appearing for paper 2 only and you are getting 30 marks then your rank expected rank would be around 17k to 19k. But you know cutoffs and ranks change every year depending on various factors like difficulty level of the papers and number of candidates appeared for the examination. So it is very difficult to predict. I appeared in WBJEE in 2017 and I score 22 in Paper 2. My rank was 21232.